The present invention relates to an isolation mount used in securing a vehicle body to a support structure, such as a vehicle cradle mount or subframe, and for absorbing vibrations and movements between the two structures.
Subframe mounts are used extensively in unibody vehicles to isolate the vibration which is transmitted from the engine to the subframe and the body. The subframe mount also improves vehicle dynamics by providing vertical stiffness, lateral stiffness and fore and aft stiffness and their respective stiffness rates. The operator of the vehicle perceives that vibration isolation relates to ride quality and that improved vehicle dynamics translates into improved handling performance.
Typically, there are as many as four locations on the subframe where an isolation mount is utilized. The subframe is sandwiched between the upper portion and the lower portion of the vibration mount and the vehicle body rests on top of the upper mount. A bolt extends through an aperture in the frame and the isolation mount. The lower mount and the upper mount are connected by a cage nut on the body to complete the attachment of the body to the subframe. The mount isolates engine or transmission induced vibration that is transmitted along the subframe to the body. The mount also improves vehicle dynamics by controlling or attenuating the relative movement between the vehicle body and subframe in the vertical mode or plane, that is up and down, relative movement, and also to control lateral mode or plane, that is side to side movement, and fore and aft mode or plane, that is front to back relative movement.
A typical design of a subframe isolation mount employs a relatively hard or high durometer rubber (typically 40 to 80 Shore A) as an isolating material. High durometer rubber for cradle or subframe mounts is an excellent material for improved handling in the lateral plane, especially when it is combined with rate plates to stiffen the response in the lateral plane and to a limited degree the fore and aft plane. However, since the solid elastomeric material is generally very stiff, it does not control or attenuate vertical forces from the subframe to the body very effectively. As a result, the isolation mount has a high lateral stiffness rate response which is desirable but a fore and aft stiffness rate response which is moderately acceptable and vertical stiffness rate response which is low. Therefore, good ride and handling of a vehicle are compromised because of the stiffness properties of the solid elastomeric material.
Thus, there is a need for a vibration isolation mount that provides for ride quality that is satisfactory to the operator without sacrificing the handling characteristics of the vehicle in the lateral plane, fore and aft plane and vertical plane. Additionally, there is a need for a mount that is lighter in weight, improves durability and reduces both initial and high mileage noise, vibration, and harshness between a subframe and a body.
The present invention discloses a one piece formed elastomeric isolation mount for motor vehicles The motor vehicle has a body portion and a subframe portion. The subframe has a through hole. The isolation mount includes a thimble member having a flanged portion and an axially extending tube portion. An annular foamed elastomeric member is adjacent to the thimble member. The annular member having a radially outwardly extending one end portion, an opposite end portion and an inner passage. The opposite end portion is acceptable in a slidable fit into the through hole from one side of the subframe portion to the other side. The opposite end portion being movable radially outwardly when the opposite end is axially advanced past said through hole and said one end portion being axially advanced to be adjacent to the one side of the subframe portion. The length of the annular member is related to the length of the through hole so that when the tube portion is inserted into the inner passage at the opposite end portion, the thimble member advances axially toward the one end and the flanged member compresses the radially outwardly potion until the end of the tube portion is adjacent to the one end portion of the annular member.
It is an object of the present invention to provide a one piece formed elastomeric isolation mount which attenuates the vibration transmitted from the subframe to the body as well as providing vertical mode, lateral mode, and fore and aft mode stiffness for improved vehicle dynamics.
These and other features of the present invention will become apparent from the subsequent descriptions and drawings.